An electronic synaptic device includes: a lower electrode; an upper electrode; and an active layer provided between the lower electrode and the upper electrode and including a plurality of conductive nanoparticles, wherein the conductive nanoparticles are dispersed in a matrix forming a continuous phase, and the matrix is composed of a protein. The electronic synaptic device has a low switching operation voltage, is capable of implementing a transition phenomenon from a short term potentiation state to a long term potentiation state even with a relatively low voltage, and has high stability; and, therefore, can be preferably applied as a memristive device for implementing neuromorphic computing.